Effects of the Electrodes’ Shape and Graphite Quality on the Arc Stability During Hydrogen Plasma Smelting Reduction of Iron Ores

• Published in: Steel research international 2023-07, Vol.94 (7), p.n/a
• Main Authors: Ernst, Daniel, Zarl, Michael Andreas, Farkas, Manuel Andreas, Schenk, Johannes
• Format: Article
• Language: English
• Subjects: arc stability; Carbon dioxide; Cathodes; electrode geometry; Electrodes; Feasibility studies; Geometry; Grain size; Graphite; Greenhouse gases; Hydrogen plasma; hydrogen plasma smelting reduction; Hydrogen reduction; Impact analysis; Iron and steel industry; iron ore; Iron ores; Metallurgy; Parameter identification; plasma; Plasma jets; Process parameters; Shape effects; Smelting reduction; Stability analysis
• ISSN: 1611-3683; 1869-344X
• DOI: 10.1002/srin.202200818

Reducing greenhouse gases (GHG), especially CO2, is necessary to counteract climate change. The European steel industry currently corresponds to 5.7% of the total EU emissions and must therefore minimize their GHG fractions in the future. One of the most promising technologies to eliminate CO2 emissions while directly reducing iron ore to steel in a single step is the hydrogen plasma smelting reduction. The stability of the plasma arc, which is determined by the properties and geometry of the graphite electrode, has a substantial impact on the process’ economic feasibility. To study the arc stability concerning the graphite quality, tip geometry, and electrode gap, a series of experiments is conducted. The results are evaluated to create stability maps and fields to identify stable process parameters. The geometry of the graphite cathode shows the primary influence on arc stability. Tips with a flat end (standard version) offering the most unstable and a machined step on the graphite cathode providing the most stable conditions. However, an additional coating to prevent side arcing leads to the deterioration of the arc. The two graphite grades tested, with different maximum grain sizes and price classes, show no great relevance to the stability of the arc. The European steel sector needs to reduce its greenhouse gas fractions. One promising technology for producing green steel in the future can be the hydrogen plasma smelting reduction (HPSR). To increase the process's economic viability, the impact of different electrode tip geometries and graphite qualities on the arc stability for the HPSR process is explored in this study.